Recovery of hydrogen sulphide



April '13 1926.

F. W. SPERR, JR RECOVERY OF HYDROGEN SULPI -I IDE Original Filed Dec. 8,1921

PatentedlApr. 13, 1926.

UNITED STATES PATENT oFrlcr...

GH, PENNSYLVANIA, /ASSIGNOB TO THE ENNSYLVANIA, A CORPORATION 01 PENN- RECOVERY OF HYDROGEN SULPHIDE.

Apphcationflled December 8, 1921,8eria1 No. 520,810. Renewed To all whom it may concern: Be it known that I, FREDERICK J r., a citizen of the United States, residing in Pittsburgh, in the county of Allegheny 5 and State of Pennsylvania, have, invented a new and useful Improvement in Recovery of Hydrogen Sulphide,"ofn which-the following is aspecification. This invention relates to the manufacture 1 of hydrogengsulphide and has for, an object toproduce concentrated or substantially pure hydrogen sulphide from gases which contain it. The process of the invention is especially applicable to the treatment of gases which contain but moderate amounts of carbon dioxide in proportion to the hydrogen sulphide content. ,A typical example of such gases is the'gas produced inthe distillation and cracking of petroleum, as this gas may contain or more of hydrogen sulphide by volume, but very little or no carbon dioxide. The process is, however, also applicable to the treatment of other gases, such as coke oven gas, produced or treated in such a manner asv to have a relatively moderate content of carbon dioxide. It is a purpose of the invention to treat gases, such as those above mentioned, in'such a way .as to remove part or all of their hydrogen sulphide content and to recover the thus removed hydrogen sulphidein a cone ntrated form, so that it may be employed or any desired purpose, for example, for the manufacture ofv sulphuric acid.-

In addition to the general objects'recite'd above, the invention has for further objects I such other improvements or advantages in operation or results as 'a in the apparatus and processes hereinafter described or claimed.

In the accompanying drawing, forming a part of this specification and showing, for urposes of exemplification, a pre erred ibrm 'and manner in which the invention W. SPERR,

re found to obtain may be embodied and practiced, but with-.

illustrates a diagrammatic rep:

July 3, 1925.

V ployed a suspension of alkaline earth hydroxides or sulphides, the principle involved n the treatment of the gas being the .same 1n each case as will be' understood from the ensuing description. Calcium hydroxide (Ca(OH) and calicum sulphide (Gas)- nray be taken'as examples of material suitable for carrying out the process; however, 00 it will be understood that the hydroxides p and sulphides of magnesium, barium, and strontium may also be employed. Calcium and magnesium compounds have the advantage of cheapness.

The process is of especial advantage inap-v plication to gases low in carbon dioxide but. is not necessarily limited to such gases. In" fact, it is'well suited to the treatment of gases containing moderate amounts of car- 0 bon dioxide. The carbon dioxide acts upon the calcium hydroxide or sulphide forming calcium carbonate which is practically insoluble and inert and does not interfere;-

either with the removal of hydrogen sulphide orits recovery in'a substantiallyv pure orm.

Calcium hydroxide and calcium sulphide have rather low solubility in water, but readily form suspension I ily with hydrogen sulphide. The calcium hydroxide 'suspensionis ordinary milk of lime. If a calcium hydroxide suspension be brought into contact with gas containingzhy drogen sulphide, the following reaction occurs:'

\Vhen the resulting suspension isheated, two reactions occur. The calcium hydrosulphide (Ca(HS) first decomposes. nto-the sul-. phicle v(CaS), as follows: 1

Part of the calcium sulphide is further d e-": composed into the hydroxide as follows;

11 both reactions, hydrogen sulphide is The resulting suspension, after heating, inay consist almost entirely of calcium sulphide or may be a mixture of sul- 'phide and hydroxide, depending upon the extent to which the heating has been carried.

I evolved.

s which react readthe hydrogen sulphide bearing gas.

-tus for. carrying will be understood that many modifications 'emulsiohs; Ascrubberof this through the power connection In any case, the suspension when cooled may be used toabsorb hydrogen sulphide from additional quantities of gas, the calcium hydroxide reacting with the hydrogen sulphide in the manner described above, and the calcium sulphide reacting as follows:

CaS+H S=Ca (HS) 2 In accordance with the invention, there is thus developed a continuous cyclic proc ess for the removal of hydrogen sulphide from gas, with recovery of the hydrogen sulphide in concentrated form. In carrying out such a process the gas may be treated with calcium hydroxide, a mixture of both, in suspension in water. The suspension containing the absorbed hydrogen sulphide may then be heated to cause it to'give up the hydrogen sulphide and to regenerate the suspension for further absorption of hydrogen sulphide. After heating the regenerated suspension is cooled and recirculated to bring it again in contact Xith 3 loss ofmaterial, whether mechanically or through secondary reactions, such as the formation of calcium'carbo'nate, may. be made up by adding to the system either'calc'ium sul hide, calcium hydroxide orboth;

e accompanying drawing illustrates 'diagrammatically one arrangement of appara- Out the process, although it and many other arrangements of apparatus may be employed. The gas containing hydrogen sulphide may be treated in a rota for the treatment of gas wit suspensions or a casing divided into compartments by trays having central openings, with rotating bells B in each compartment which to the shaft 0, the latterbeing driven D by a motor E. The gas containing hydrogen sulphide enters the bottom of the scrubber through 2 however, is 5 'i lfii'droxide to 100 parts by'weight of water. "i

the pipe F and passes through compartments, in countercurrent tothe suspenslon, and emerges through the pipe G. .50

plytank'H through the-pipe line I and dischar s 'into "the top the different The suspension (such as a water suspension of calcium hydroxide) is drawn from the su compartment. of the Suspensions parts by weight of calcium .e' suspension containing the absorbed hydrogen sulphide flows out of the scrubber d the tank K. Here through the pipe J into i it may be kept in agitation by airor steam blown through the pipe 'L. From the tank K, the suspension is pumped'through the. .line; M into the preheater N where it is heated-- by the 1 steam .and gases from the calcium sulphide or type embodies are attachedof different strengths maybe-employed a satisfactory suspension,

evaporators.

1? until this is full and then into P The first evaporator is heated to the boiling point' and hydrogen sulp'hide is rapidly, evolved, passing through the pipe'Q into the line B which is connected with a coil in the preheater N. The cooling-eifect of the preheater maybe supplemented by a condenser in which the vapors are further cooled by fresh air. The steam is condensed and the condensate, carrying a little hydrogen sulphide, runs intotlie tank S, from which the condensate may be returned through the line T to the' tank' K. The bulk of the hydrogen sulphide passes out through the line, U and may be utilized as desired, e. g., for the manufacture of sulphuric acid orsulphur.

Wh have been sufliciently heated so that all of the calcium hydrosulphide is decomposed to form calcium sulphide together with some hydroxide, theheating is discontinued and the valve in the line Q, is closed. Valve V is opened and the contents of the evapo- Fator are allowed. tank W, provided with cooling coils through this tank are preferably kept in agitation by air or by mechanical means. In other ar 'y rangements, the hot suspension from the gas scrubberA which is es ecially adapted evaporator may be usedcto assist in preheating the suspension going to the evaporators. In the meantime, evaporator P, will be filled and heated, the hydrogen sulphide and steam passing out through the lineQ The operations of filling, heating and emptying are conducted alternately rators. It is advantageous to employ vacuthe operation of heating since,the removal of hydrogen sulphide is greatly, facilitated thereby. Steam directly injected .infto the contentsiof the-evaporator also assists in accelerating'igthe' reactions. The. expulsion: of hydrogen; sulphide from the susaei'litatedfby hrough -paratus.. .From the cooling is pumped through thelineXtdthe tank H rom which it is circulated again over the gas in the 'scrubberJAJ ,-As the suspension iininishe's in efficiency through" the formation of calcillm carbonate or otherwise, part of it may be periodically removed from the stem and replaced by fresh calcium hyroxide added to tank Calcium sulhide may be employed instead offcalcium ydroxide for this purpose.

passing air 'orother. gases the suspension, in the heating app pensionduring"theRheating may also be which water is circulated. The contents of tank suspension I en the contents of the evaporator P to drain into the cooling 1 in, the two evapoa The invention as hereinabove set forth drogen-sulphide bearing may be variously embodied within the scope with a suspension of an alkaline earth comof the claims hereinafter made. pound having an alkaline reaction to ah- I clann: sorb the hydrogen sulphide from the gas;

' drogen-sulphide 'ment stage;

I the hydrogen sulphide and to regenerate the absorb the hydrogen then subjectln the suspension containing the absorbed hydrogen sulphide to a preheating operation; then heating the preheated sus- 'on to expel the hydrogen 'to regenerate the suspension; the liberated vapo'r being employed for preheating the suspension going to the heating operation; and eoolin the regenerated suspension and assing it ack to the gas substantially as specified. v

5. The process of producing hydro en sulphide which consists in: passing a ydrogen-sulphi'de bearing gas into contact with a suspension of calcium hydroxide to absorb the hydrogen sulphide from the gas; and then subjecting ing the abso 'bed hydrogen sulphide to a heating operation to liberate the hydrogen sulphide and to regenerate the suspension for further from gases; substantially as specified.

6. The process of producing hydro en sulphide which consists in: passing a ydrogen-sulphide bearing as into contact .with a suspension of; cium compound having an alkaline reaction to absorb the hydrogen sulphide from the gas; and then crating the suspension containing the absorbed hydrogen sulphide for further absorption of hydrogen sulphide by subjecting said suspension to a heating operation to liberate the absorbed hydrogen sulphide; substantially as specified. I p

7. The process of producing hydro en sulphide which consists in: pasing ydrrigeu-sulphide, into contact m .a suspe f alkaline earth compound having-an reaction to absorb the hydrogen andthen regenera the sulphide from the gas; then subjecting the suspension containing the absorbed hydrogen sulphide to a preheating operation; their heating the preheated suspension to expel suspension; the liberated vapor being employed for preheating the suspension going to the heating operation; and cooling the regenerated suspension and passing it back to the gas treatment stage; substantially as process. of producing hydrogen which consists in: passing a hybeaIing into contact with a suspension of calcium hydroxide to sulphide from the gas; then subjecting the suspension containing the absorbed hydrogen sulphide to a preheating operation; then heating the preheated 'on to expel the hydrogen sulphide and to regenerate the suspension; the liberated vapor heating the suspension going to the heating operation; and cooling the regenerated suspension and passing it back to the gas treatsubstan 'ally as 3. The process of producing hydrogen sulphide, which consists in: passing a hydrogen-sulphide bearing gas into contact suspension of calcium compound an alkaline reaction to' absorb the from the gas; then subion containing the ab- 2. The sulphide,

SUSPODSIOII' confurther absorption of hydrogen sulphid reheatmg th subjecting said on heating o'peratlon; oration to liberate the suspension and sulphide; substantially as to the gas treatment stage In testimony whereof I have hereunto set substantially-as 1 my haml- -i 4.The rpeesot'producinghy u sulphide, w eonsld m: assing a yasingit V rnnnnnicx w. srnna, J

into contact sulphide from the gas;-

I sulphide and treatment stage;

the suspension contain- I absorption of hydrogen sulphide taining the absorbed ydrogen sulphide flor y to a heating opthe absorbed hydrogen 

